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<p>The Indonesian Throughflow (ITF) plays important roles in global ocean circulation and climate systems. Previous studies suggested the ITF interannual variability is driven by both the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) events. The detailed processes of ENSO and/or IOD induced anomalies impacting on the ITF, however, are still not clear. In this study, this issue is investigated through causal relation, statistical, and dynamical analyses based on satellite observation. The results show that the driven mechanisms of ENSO on the ITF include two aspects. Firstly, the ENSO related wind field anomalies driven anomalous cyclonic ocean circulation in the western Pacific, and off equatorial upwelling Rossby waves propagating westward to arrive at the western boundary of the Pacific, both tend to induce negative Sea Surface Height Anomalies (SSHA) in the western Pacific, favoring ITF reduction since the develop of the El Niño through the following year. Secondly, the ENSO events modulate equatorial Indian Ocean zonal winds through Walker Circulation, which in turn trigger eastward propagating upwelling Kelvin waves and westward propagating downwelling Rossby waves. The Rossby waves are reflected into downwelling Kelvin waves, which then propagate eastward along the equator and the Sumatra-Java coast in the Indian Ocean. As a result, the wave dynamics tend to generate negative (positive) SSHA in the eastern Indian Ocean, and thus enhance (reduce) the ITF transport with time lag of 0–6 months (9–12 months), respectively. Under the IOD condition, the wave dynamics also tend to enhance the ITF in the positive IOD year, and reduce the ITF in the following year.</p>

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Interannual variability of surface Indonesian Throughflow and its relationships with Pacific and Indian Oceans derived from satellite observation

  • 期刊论文

  • 发表日期：

    2025年1月1日

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  • Yingyi Yang,
  • Tengfei Xu,
  • Zexun Wei,
  • Dingqi Wang,
  • Zhongrui Cai,
  • Yunzhuo Zhang,
  • Yongshun Ma

摘要

The Indonesian Throughflow (ITF) plays important roles in global ocean circulation and climate systems. Previous studies suggested the ITF interannual variability is driven by both the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) events. The detailed processes of ENSO and/or IOD induced anomalies impacting on the ITF, however, are still not clear. In this study, this issue is investigated through causal relation, statistical, and dynamical analyses based on satellite observation. The results show that the driven mechanisms of ENSO on the ITF include two aspects. Firstly, the ENSO related wind field anomalies driven anomalous cyclonic ocean circulation in the western Pacific, and off equatorial upwelling Rossby waves propagating westward to arrive at the western boundary of the Pacific, both tend to induce negative Sea Surface Height Anomalies (SSHA) in the western Pacific, favoring ITF reduction since the develop of the El Niño through the following year. Secondly, the ENSO events modulate equatorial Indian Ocean zonal winds through Walker Circulation, which in turn trigger eastward propagating upwelling Kelvin waves and westward propagating downwelling Rossby waves. The Rossby waves are reflected into downwelling Kelvin waves, which then propagate eastward along the equator and the Sumatra-Java coast in the Indian Ocean. As a result, the wave dynamics tend to generate negative (positive) SSHA in the eastern Indian Ocean, and thus enhance (reduce) the ITF transport with time lag of 0–6 months (9–12 months), respectively. Under the IOD condition, the wave dynamics also tend to enhance the ITF in the positive IOD year, and reduce the ITF in the following year.